| 摘要 |
PROBLEM TO BE SOLVED: To reduce the space occupied by a speed reduction gear mechanism by using a practicable worm gear by providing the speed reduction gear mechanism with three or more sets of worm gears and providing multiple thread ridges on one or more of the worms. SOLUTION: A speed reduction gear mechanism 19 is provided between a support shaft 5a of a door stay 5 and an electric motor 18, and the speed reduction gear mechanism 19 is stored in a gear chamber 16. The speed reduction gear mechanism 19 includes a first to a third worm gears 20, 21, 22. The first worm gear 29 is formed by a first worm 23 provided on the output shaft of the electric motor 18 and a first worm wheel 24 meshing with the first worm 23, and the first worm 23 is formed as a multiple-thread worm which has many, such as three thread ridges.
|
